Science explained with humor, analogy, and pop culture. (Because sometimes you just wanna understand a thing…)

Why the Burning? The Secrets of Hydrogen Peroxide and Alcohol

In it together – how? Why?

by chelsea schuyler

Hydrogen Peroxide Kills Stuff

Feel the burn! Ever get a cut and feel the need to apply first aid like the good scout you are? You might have a choice between two uncomfortable choices, both will feel like burning: Hydgrogen peroxide and isopropyl alcohol.

But in actuality, only one of these things is actually doing any damage. The other is an illusion of sorts….

I was recently experimenting, with hydrogen peroxide and yeast to make the ever foamy and explodey ‘elephant toothpaste’, (see my other blog)

Elephant toothpaste: “Okay elephants, twice a day now.”

I was using highly concentrated hydrogen peroxide, and got some on my thumb.

Finger death, now in pearly white

After a bit of a delay, I realized my thumb had turned white and felt like a friction burn, slowly increasing in pain.

What was happening? Hydrogen peroxide was bursting my very cells open.

” ‘Twas Hindenburg peroxide killed the beast”

Now, hydrogen peroxide’s been used as a first aid ingredient for decades because it kills the bad stuff. Technically, it destroys the cell walls of bacteria, leaving them to explode a la Hindenburg.

However, since apparently it bursts your own living tissue as well, possibly best to just clean your wound with soap and water and let your immune system handle it.

In fact, the immune system is actually using hydrogen peroxide already – our bodies make it! (Those cheapskates at Safeway…)

Hydrogen Peroxide in Your Immune System

When you get cut, your body’s hydrogen peroxide comes to the wound, signaling white blood cells, which come an average of 17 minutes later as the major backup that saves the day. If hydrogen peroxide is Jon Snow’s army, white blood cells are Sansa’s knights in the Battle of the Bastards.

Because flames

While hydrogen peroxide can do some damage, white blood cells spew out a medley of destroyers, including more hydrogen peroxide, but lots of other stuff too. It’s basically a weapons upgrade from the default gun to the flamethrower in, well, all video games.

Keeping Hydrogen Peroxide at Bay

Wait, how do we keep hydrogen peroxide in our bodies if it’s a walking cell-bomb? Well, first, we isolate it into little packages in our cells called peroxisomes. There, we also make an enzyme (catalase) that keeps immobilizes it by splitting hydrogen peroxide (2H2O2) into water and oxygen (2H2O and O2).

“Do I have to separate you two?”This image – lopping since 1860

Hydrogen peroxide breaks down into water and oxygen naturally, but this enzyme speeds up that process, resulting in oxygen bubbles flying out everywhere.

It’s like the difference between waiting for soldiers to starve to death vs. sending a single samurai to lop heads off until they’re a more amenable collection of heads and bodies.

Catalase: because in science all enzymes look like confetti and silly string

Ever get a blood stain on your shirt? A great trick is to put hydrogen peroxide on it and watch the alka seltzery chemical reaction of fizzy goodness. Bonus: the stain will disappear!

Blood has catalase in it, so it reacts to the hydrogen peroxide, and all those oxygen heads are separated from water bodies, making the little bubbles you see. A water stain is left instead, which evaporates.

Why We Go Gray:

Fun fact – as we age our catalase production factories wear down, and less of it is made. This leaves excess hydrogen peroxide free to wreak havoc…at least in hair cells.

Melanin gives our hair its color, but without its samurai catalase protector, hydrogen peroxide moves in and breaks it down. This is partly why our hair turns grey as we age.

Weirdly though, pouring hydrogen peroxide on you doesn’t really sting (at least, if you’re using the regular kind from the grocery store, the 3%. The elephant toothpaste required 12%). You might be thinking instead of the sting-sation of alcohol.

Alcohol – It Burns!! Except Not

Go ahead, use whatever. It all hates you.

Once again, if you cut yourself (stop doing that) and decide to clean the wound with rubbing alcohol, you will feel a burning. But rubbing alcohol isn’t like hydrogen peroxide – it’s not doing any actual damage.

It’s actually similar to what happens when you swallow hard liquor (ethanol – different chemical makeup, but similar enough) – that burning in your throat isn’t an actual burn.

The alcohol is actually tricking your body into thinking there should be pain there.

VR1 Receptors Will Believe Anything

If you want to know what the weather’s like, but you’re stuck in a dark room somewhere, your friend might stick their hand out the window and report back about whether it’s hot, cold, misting, wind-chilled, or humid.

Well, your body (and throat) has what is basically a bajillion little arms sticking out of windows, reaching out to see what’s happenin, and reporting back to the brain.

Dear brain: it’s dark and unsettlingly cartoony

If something over about 107 degrees touches you, the VR1s tell the brain “HEY – things are really heatin up in here.” And the brain goes “That must be painful. I mean literally, I shall make that painful.”

Well, ethanol reduces a VR1’s temperature threshold to 93 degrees, so when you pour that isopropyl on that wound, your body is confused and registers its own body heat (98.6) as burning.

If you say ‘gullible’ really slow it sounds like ‘oranges’

It then runs off tattle-taling to the brain going “FIRE FIRE!” and your brain goes “AAAH!!” when in actuality, nothing is happening. Except that your uncle’s Scotch has just turned your throat into a scourge of screaming throat-hands.